This study intended to evaluate classical musicians' risk of hearing loss. We studied 63 musicians from four Helsinki classical orchestras. We measured their hearing loss with an audiometer, found their prior amount of exposure to sound and some individual susceptibility factors with a questionnaire, measured their present sound exposure with dosimeters, and tested their blood pressure and cholesterol levels, then compared their hearing loss to ISO 1999-1990's predictions. The musicians' hearing loss distribution corresponded to that of the general population, but highly exposed musicians had greater hearing loss at frequencies over 3 kHz than less-exposed ones. Their individual susceptibly factors were low. Music deteriorates hearing, but by less than what ISO 1999-1990 predicted. The low number of individual susceptibility factors explained the difference, but only reduced hearing loss and not the prevalence of tinnitus.

The sound levels to which orchestra musicians are exposed depend on their instrument, the composition being played, and the players' physical location within their orchestras. Typical sound levels in string sections are 86-91 dB(A), [1],[2],[3] 90-94 dB(A) in woodwind sections, 83-94 dB(A) in brass sections, and up to 98 dB in percussion sections. Musicians are also exposed to high sound levels during personal and group rehearsals, and are likely to spend considerably more time in rehearsals than in performances. [1] The total amount of noise exposure indicates the likelihood of an elevated risk of noise-induced hearing loss (NIHL). [1]

However, orchestra musicians' hearing is apparently better than what their exposure to sound would suggest. Arnold and Miskolczy-Fodor [4] found no hearing loss among 30 professional pianists, and indeed, few studies have found changes in audiogram readings which could be interpreted to have been caused by exposure to sound, and whatever changes have been found are small. Westmore and Eversden [5] found hearing loss in 23 of 68 ears, but this hearing loss was greater than 20 dB in only four of them.

Royster et al. [6] measured the noise exposure and hearing thresholds of Chicago Symphony Orchestra musicians and found the sound levels to be at 75-95 dB(A), corresponding to an 8-h daily Leq , and although the musicians' mean hearing thresholds of 59 dB were better than those of an unscreened non-industrial population, 52.5% of the individual musicians showed notched audiograms consistent with NIHL. When testing the hearing of musicians with high-frequency audiometry, Johnson et al. [7] found no difference between 60 musicians and 30 subjects from a non-noise-exposed population.

When comparing musicians in the same orchestra, McBride et al. [8] found that those musicians exposed to a higher level of sound had greater hearing loss than those exposed to lesser levels. Axelsson and Lindgren [9] measured the sound levels in two theaters and the hearing thresholds of 139 musicians and found that the sound levels varied from 83 to 92 dB(A), with the highest levels being in the orchestra pit, and that 59 musicians had worse hearing than usual for their ages. However, Jansson and Karlsson [10] and Kδhδri et al.[11] found that the hearing of orchestra musicians does not differ from the hearing of the normal, non-exposed population.

When referring to these small threshold shifts, many authors conclude that music is less damaging than industrial noise [12],[13],[14] but this ignores the higher incidence of tinnitus and hyperacusis among musicians, [15] and may be a result of low susceptibility to noise due to healthy lifestyles, as indicated by a low number of such individual susceptibility factors as the use of painkillers, elevated blood pressure, elevated cholesterol, the presence of white-finger syndrome, and smoking, [16] the factors which seem to increase the risk of hearing loss if several of them are present. [17]

The purpose of the study was a) to evaluate the risk of NIHL among orchestra musicians, b) to compare the observed NIHL to the prediction of ISO 1999 (1990), and c) to find the role of individual susceptibility factors in the onset of hearing loss among orchestra musicians.

Methods

Sample

The sample consisted of the members of four major orchestras from the Helsinki metropolitan area, the National Opera Orchestra, the Tapiola Sinfonietta Symphony Orchestra, the Radio Symphony Orchestra, and a military brass band called the Guards. Inclusion in the sample was based on voluntary participation, the subjects' audiometry corresponding to normal NIHL audiometry with the notch at 3-6 kHz, and their having no ear or central nervous system (CNS) infections.

Altogether, 67 musicians participated in the study, of whom we excluded four because of their audiometer form, with 38 males with a mean age of 41 ± 9 years, and 25 females with a mean age of 40 ± 6 years.

We informed the members of the sample about the purpose of the study before presenting them with the questionnaire.

Noise susceptibility

We measured the cholestrol values of the sample members' blood samples and their bloodpressure using Omron M-9 instrument, and obtained data about their smoking and use of painkillers with a standard questionnaire which also had questions on information about all their other exposure to noise through such activities as teaching and noisy hobbies. The questionnaire also asked about the exclusion criteria of recurrent ear and CNS infections. We scored their noise susceptibility as the number of risk factors exceeding the limit values, as shown in [Table 1]. [16]

We measured the audiograms using a Madsen Midimate 602 clinical audiometer, starting with the subjects' right ears in the sequence of 1000, 2000, 3000, 4000, 6000, 8000, 500, and 250 Hz, and then repeating the process with their left ears. We conducted all audiometer measurements in the audiometric booth of the occupational-health care unit except for the members of the Guard band, in whom we measured in a booth at the Finnish Institute of Occupational Health.

Tinnitus and hyperacusis

We obtained this study's data about the presence of tinnitus and hyperacusis after rehearsals and performances with questionnaire items with a 5-point Likert scale of never, seldom, sometimes, often, always.

Exposure evaluation

We conducted these measurements by instrument group in one to four different sessions, each using a dosimeter (Larson and Davis 705, 706), placing the microphone on each musician's shoulder in such a way that it did not disturb the performance. Each dosimeter recording took place over an entire training or performance session, providing us with a total of 130 measurements from performances, group rehearsals, and individual rehearsals. We calculated the annual exposure using the following formula:

The ISO 1999-1990 models consist of two Gaussian distributions, one for over the 50th percentile and another for under the 50th percentile. Age, gender, and noise exposure are the input parameters. [18] As a result, the Z-score distribution of observed threshold shifts has zero means and standard deviations of one.

We applied the Z-scoring to the audiograms twice. To compare the musicians' hearing to the hearing of the non-noise-exposed population, we set the noise-exposure term to zero. We inserted the noise-exposure term in the second transformation, which enabled comparison to noise-exposed industrial workers. We calculated the Z scores using Matlab 7 rev 3, made by Mathworks Inc., USA, and sent the results to SPSS 17, made by SPSS Inc., USA. We then made the comparisons using t-test and analysis of variance (ANOVA).

Results

[Table 2] shows the results of the sound exposure measurements. Most of the musicians are exposed to sound levels over 90 dB (A). Those in the Guard band received the highest exposure and those in the Tapiola Sinfonietta, the smallest orchestra, received the lowest.

The exposure time was long, with 12% of the subjects having started their professional career before age 20 years, the mean starting age being 23 years. The total exposure was somewhat higher among men (101.5 ± 5.3 dB) than among women (98 ± 5 dB). The difference was due to higher weekly exposure (90 ± 5 dB vs. 87 ± 3 dB) and longer exposure time (19 ± 101 vs. 15 ± 8).

The mean hearing loss was remarkably symmetric, but somewhat higher in the left ear [Figure 1]. The hearing loss was tuned to the higher frequencies, which is typical for NIHL and presbycusis. The greatest hearing loss was typically found at 6 kHz, as shown in [Figure 1].

Figure 1: Mean hearing loss by frequency in right (r) and left (L) ear by frequency

To test whether this hearing loss depends on exposure, we divided the musicians into a high-exposure class (Lex > 100) and a low-exposure class (Lex < 100). In the high-exposure class, the age-corrected hearing loss was significantly higher in both the ears at frequencies of 1000-6000 Hz except for the left ear at 4000 Hz where only a trend (P<0.07) was seen. The results are shown in [Table 3]. The exception in the right ear at 4 kHz is probably due to the relatively large variation at this frequency.

Comparing the musicians to a non-exposed population using Z-scoring revealed that their hearing loss corresponded to the expected hearing loss of that non-exposed population, except for at 3000 and 6000 Hz. At 6000 Hz, the hearing loss was higher than predicted, as shown in [Figure 2].

Figure 2: Comparison of the musicians' hearing loss to that of a non-exposed population. Zero corresponds to the expected value. Circles present outliers (95% confidence interval)

The musicians' hearing loss can be seen to be smaller than expected for the frequencies of 2000, 3000, and 4000 Hz (P< 0.04), with an expected value of 6000 Hz (NS), when compared to an industrial population also having had lifetime exposure, as shown in [Figure 3].

Figure 3: Comparison of the musicians' hearing loss to a population with the same lifetime exposure. Zero corresponds to the expected value. Circles present outliers (95% confidence interval)

Tinnitus and hyperacusis were relatively frequent, as shown in [Table 4], with 60% of the musicians having never or seldom experienced tinnitus after group rehearsals and performances. A greater number (78%) reported never or seldom experiencing it after personal training. Only 16% of the musicians reported never having experienced hyperacusis.

Table 4: Percentage of musicians having experienced tinnitus (tinnitus lasting more than 5 minutes at a time) or hyperacusis

The musicians' mean systolic blood pressure was 127 ± 13 mmHg, and their mean diastolic blood pressure was 80 ± 10 mmHg. Their mean cholesterol value was 4.8 ± 0.8. We also found that 12% of the subjects were current smokers, 2% were former smokers who had stopped, and 10% had used painkillers regularly for more than 5 years. The number of risk factors also increased with age, as shown in [Figure 4], with the regression line at 0.0875 + 0.0001 × age. The expected number of risk factors was therefore one at the age of 60 years, and their hearing did not depend on the number of risk factors, mostly because only 8% of the subjects had three or more of them, which made the high-risk group too small for comparison.

The issue of whether musicians tend to have NIHL has been debated for a long time. This study found that orchestra musicians' hearing loss corresponds to that of the non-noise-exposed population, according to ISO-1999. [18] However, it also found that the extent of hearing loss depends on the degree of exposure to high-volume sound, similar to what Kuronen et al. [19] found for military pilots.

NIHL is a complex disorder that is influenced by both environmental and genetic factors. As such, it varies considerably between individuals. The environmental factors involved in NIHL have been studied relatively extensively. Noise itself is the most studied and best-documented environmental factor causing hearing loss, as it can cause mechanical damage, exert metabolic effects on the inner ear, or both. [20],[21] Co-exposure to organic solvents and heavy metals is among the environmental factors known to cause a raised susceptibility to noise. Authors [20],[21],[22],[23],[24] found a synergistic effect between noise exposure and exposure to chemicals in laboratory animals. Such additional environmental factors as ototoxic substances, drugs, heat, nutrient disturbances, and vibrations can also influence susceptibility to NIHL. [25] Furthermore, studies such as that of Toppila et al. [17] have found that individual factors such as smoking, elevated blood pressure, and cholesterol levels may influence the degree of NIHL.

This study sample's low degree of NIHL can therefore be explained by the presence of a non-hostile working environment and various individual factors. The musicians' working environment has no ototoxic chemicals or vibrations, which is an indication that it is relatively friendly. Their number of individual risk factors is small and we observed no age dependency. Age dependency is high for blue-collar workers and small for military pilots. [19] This leaves the major question of why the number of risk factors is so low, and it seems reasonable to speculate that this may be due to the nature of the work. Musicians need to concentrate intensely during all performances, which in turn requires physical fitness, creating an incentive for regular, healthy life habits, as this study's finding of a low number of risk factors among them has shown.

Another factor indicating that music can harm musicians' hearing is the sample's elevated prevalence of tinnitus and hyperacusis. The low presence of hearing loss and the high presence of tinnitus can be explained by their etiology. Overstimulation may lead to cochlear injury either mechanically or metabolically, which are two fundamentally different ways. [26]

At sound-pressure levels (SPLs) of less than 125 dB, sound-induced overstimulation and overactivity of the cochlea can result in disturbed cochlear homeostasis and subsequent functional impairment in the absence of direct and immediate mechanical damage. Experimental evidence suggests a critical level about 125 dB SPL, at which the cause of damage changes from predominantly metabolic to mechanical. [27] Tinnitus, however, is more common among people exposed to such impulsive noise as music. [28] Impulsive noise's high peak levels indicate that mechanical damage plays an important role in the etiology of tinnitus. It is reasonable to assume that risk factors affect the effects of metabolic trauma but not those of mechanical trauma, which could explain the low prevalence of NIHL and the high prevalence of tinnitus among musicians.

Taking into account the risk of hearing loss, tinnitus, and other symptoms, the use of hearing protectors would seem to be justified. Musicians have said that their main reason for using them is a fear of hearing loss and tinnitus, [1] but they also used them to avoid pain, to protect their ears from fatigue, to decrease stress, irritation, and fatigue, and due to existing hearing loss and tinnitus. However, it seems that for many of the problems created by wearing hearing-protection devices, especially such devices' effect on their performances were worse than their fears of hearing loss, a factor which limits their usage of such devices. Musicians have reported that having existing hearing loss especially makes the use of hearing protectors difficult. [1] It would therefore be advantageous for musicians to start wearing hearing protectors as early as possible, especially before symptoms appear.

Conclusions

The hearing of classical musicians corresponds to that of the non-noise-exposed population according to ISO-1999:1990. [18] Hearing loss is nevertheless dependent on exposure to noise, and classical musicians do suffer from a high rate of tinnitus and hyperacusis. Their low noise susceptibility is due to a low incidence of risk factors and is probably due to a low rate of exposure to negative environmental factors.